The earliest known cardiovascular system dates to 520 million years ago

Blood evolved many times over hundreds of millions of years

The earliest evidence of a blood-like substance comes from ancient arthropods, which appear to have had copper-based blood. In the 500 million years since then, some creatures have grown to rely on other variants, such as humanity's iron-based blood.

Evidence of cancer has been found in a 1.7-million-year-old fossil

Cancer has existed as long as humans have, with some of the earliest evidence found among fossilized bone tumors, human mummies in ancient Egypt, and ancient manuscripts. The oldest example was uncovered in a toe—millions of years old—from an ancestor of modern-day humans.

An interactive guide to the cardiovascular system

The cardiovascular or circulatory system moves blood throughout the body, ensuring cells have necessary nutrients and removing any waste. Click through this interactive 3D guide to explore the system as it crisscrosses the body via arteries, veins, and capillaries. This guide also includes similar breakdowns of the body and its other processes.

Cell theory originated from microscopic observations of cork and dental plaque

In the mid-1600s, Robert Hooke identified compartment-like structures—which he called cells—in cork, and Anton van Leeuwenhoek discovered bacteria in samples of his dental scrapings. Almost 200 years later, Matthias Schleiden and Theodor Schwann showed that plants and animals, respectively, are composed of cells, proving that cells are the foundation of all living things.

The first appearance of bioluminescence was at least 540 million years ago

After analyzing fossils, genetic data, and statistical methods, scientists believe octocorals were the first organisms to evolve light-producing abilities. As a result of independent evolution across at least 94 species, this phenomenon is connected to a diverse range of behaviors.

The economics of horseshoe crab blood

Horseshoe crabs are older than dinosaurs and have survived five mass extinctions that wiped most life from the planet. But it's only now that their future as a species is in danger. This blood, worth about $60,000 per gallon, is hyper-sensitized to certain bacteria that are fatal to humans. This 17-minute podcast dives into humanity's pursuit of horseshoe crab blood, a "somewhat magical" mixture heavily relied on by the pharmaceutical industry.

Medical recognition of strokes stretches back to ancient Greece

Every minute, 750 milliliters of blood flows to the brain, supplying 20% of the body’s oxygen. A sudden disruption—whether from a clot (ischemic stroke) or a bleed (hemorrhagic stroke)—can be life-threatening. From ancient Greek theories to modern CT and MRI scans, here’s how stroke science has evolved over time.

Fossils suggest tardigrades developed cryptobiosis more than 180 million years ago

As of 2024, three tardigrade fossils have been discovered, all preserved in amber. Analysis suggests different species of the organism existed over 500 million years ago, when marine heterotardigrades and freshwater terrestrial eutardigrades diverged. (Some readers may experience a paywall.)

How the heart achieves its first beat

Scientists observed zebrafish embryos as they grew and isolated the several-second-long initial heartbeats to better understand this crucial moment in every heart's life. The zebrafish's heart starts beating 20 hours into their existence. Each heart cell activates electrically at random, without rhythm. As these cells mature, they become more sensitive to electrical charges; as they all fire, a rhythm is established and a pulse is born.

Historians estimate only 1% of shipwrecks have been discovered

The oldest known shipwreck dates to around 2,700–2,300 BCE, but evidence suggests humans started open-ocean sailing at least 50,000 years ago. Many have completely deteriorated but artifacts aboard the vessels remain, while many lack historical records of the event or location.

When did humans start kissing romantically?

This article explores the ancient roots of romantic kissing. Current archaeological evidence dates sexual and romantic lip kissing to about 2,500 BCE. A Mesopotamian clay tablet from the time shares a tale of two deities locking lips. There's also...

The Antikythera mechanism: The oldest-known analog computer

A device now considered the world's oldest computer was pulled from a shipwreck more than 120 years ago. Known as the "Antikythera Mechanism," it is now believed to have allowed precise tracking of astronomical positions, and its sophistication overturned understanding of Ancient Greek capabilities.

Pig heart valves have been placed in humans since 1965

The first successful use of a pig heart valve in a human was reported in 1965. This 2015 video details why humans have been able to use pig animal valves for so long with good results and how that differs from what's needed for whole organ transplants.

What did the earliest swords look like?

That depends on where you draw the line between daggers and swords. According to current evidence, the first swords appeared 5,000 years ago in what's now Turkey. Unfortunately, evidence of the earliest swords is colored by survivorship bias; It's...

Visualize the 5,000-year history of consumer credit in one infographic

Consumer loans for agriculture were likely first used around 3500 BCE, but modern consumer credit took many more centuries to be established. England's credit reporting system, for instance, dates back to the early 1800s when a group of English tailors began swapping information about customers who failed to settle their debts.

What a tiny marine worm can tell us about our brains

Meet the amphioxus, a small eel-like animal that has a lot to teach us about brain evolution. The genetic roots of our brains can be seen in these unusual creatures. This three-minute educational video focuses on the evolutionary history of the human brain through these odd little critters with a 500-million-year-old history.

Exploring the link between history, art, and anatomy

Throughout centuries, art has played a vital role in sharing—and furthering—scientific understanding. This largely began in 1543 when physician Andreas Vesalius worked with an artist and engraver to transform learnings from his dissections into...

Pre-coin currencies like shells were subject to counterfeiting

While it is difficult to pinpoint the very earliest form of money that was used, a type of shell called cowrie shells were used as currency as far back as 3300–2000 BCE. These shells were imitated using ivory, bone, clam shells and more.

A 15th-century university student documented a surprisingly detailed fitness plan

Modern fitness stems from the revolution in the knowledge we have of the human body, its cardiovascular systems, how muscles work, and more. Nonetheless, people through the centuries have had fitness regimes—including one university student whose fitness plan was preserved in an obscure document found between a manuscript.

The virus was officially described for the first time in 1789

Michael Underwood, an English physician and surgeon, was the first to describe the disorder, noting it caused disability in the lower extremities in children. Large-scale outbreaks of the disease were not observed until the late 19th century.

The oldest medical report of a near-death experience dates to around 1740

In 2014, Dr. Philippe Charlier, a medical doctor and archeologist, found a French medical book from 1740 that described the near-death experience of a pharmacist. Using the Greyson Scale, Charlier found that the incident would have rated at least 12/32, more than high enough to scientifically classify as an NDE by today’s standards.

A look at the Kidd Creek Mine in Canada, which houses the world's oldest isolated water

The mine sits on the Precambrian Canadian Shield—an ocean floor dating back 2.7 billion years. Exhibiting a musty smell, the water is 10 times saltier than seawater and offers insights into Earth's ancient seabed.

Climate proxies reveal past climate patterns using preserved natural evidence

Scientists use physical, chemical, and biological materials preserved in sediments, ice, and fossils to infer historical climate data. These proxies are studied and calibrated against modern climate conditions to interpret ancient environments accurately.

Synchronized swimming dates back to Ancient Rome

Known for gruesome gladiatorial contests, ancient Rome's aquatic spectacles may have been even more over-the-top. This article dives into the art of synchronized swimming in ancient Rome. Lakes were dug and amphitheaters flooded to provide space for aquatic reenactments of naval battles and artistic performances. Swimmers playing the role of water nymphs would create elaborate shapes, including ships with billowing sails.

Explore the world's oldest constitutions

The 1789 US Constitution remains the oldest active written national constitution. Older systems exist—such as San Marino’s statutes or the Magna Carta—but they are not single, codified constitutions. See how other countries compare in this visualization.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

This real-time tracking of the hantavirus cruise ship outbreak in May 2026 offers a unique glimpse into the global reach of the outbreak and whether the virus sickened passengers and their communities around the world.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

The animatronic shark from Steven Spielberg's 'Jaws,' the first modern blockbuster, was a complex underwater apparatus called 'Bruce.'

English mathematician Ada Lovelace wrote the first computer algorithm a century before computers existed and hypothesized that computing devices would one day be able to compose music—foreseeing the generative AI systems of today.

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

Stanford built a Google Maps for the Roman Empire, revealing how much it cost to travel in the ancient world

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

Planarian flatworms are small, aquatic worms with exceptional regenerative capabilities. When cut, the worms can regenerate multiple bodies in a matter of weeks.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

Trace how the Bill of Rights, inspired by centuries of political theory, took shape between 1774 and 1789.

US consumers collectively owe more than $1T to credit card companies—almost as much as they owe in auto loans.

Hear 50 years of iconic hip-hop samples, the genre's foundational looped tracks

The first image of a black hole was captured by creating an Earth-sized virtual observatory from a network of eight radio telescopes.